The Chronicle of Higher Educationrecently featured an article lamenting the lack of “diversity” in my discipline. Philosophy, so goes the article, just hasn’t been welcoming toward minorities and women.

Thankfully, such enlightened departments as that found at Penn State University have endeavored to “decolonize the canon.”

Of course, academia isn’t in the least bit interested in promoting the only diversity that can, or should, mean something in an institution of “higher learning.” Its equation of “diversity” with gender and racial representation is part of the problem.

Indeed—and I say this as someone who is an academic who happened to have grown up in a lower-middle class neighborhood in Trenton, NJ—there exists far more intellectual diversity at the corner bar than can be found in your average college or university.

Not only does the data confirm the endless anecdotal evidence that legions of academic dissidents like myself have acquired over the years. The data reveals that academics are moving even further to the left.

The most recent study available was conducted by the University of California. Its findings were released a little more than three years ago in the November of 2012 issue of Inside Higher Education.

The study identifies five ideological or political categories: “far left,” “liberal,” “middle of the road,” “conservative,” and, finally, “far right.” What it finds is that faculty of all ranks from both universities and colleges, institutions that are private and public, large and small, religious and non-religious, self-identified as “far left” to a significantly greater extent than they had just three years earlier: In 2008, 8.8% so self-identified. In 2011, that number had risen to 12.4%.

In glaring contrast, those who self-identified as “far right” dropped from—wait for it—0.7% to 0.4%.

However, these numbers alone grossly understate the hegemonic rule of leftist thought among faculty on college campuses, for the same study found that the number of self-identified “liberals” increased from 47.0% to 50.3%. Meanwhile, those in “the middle of the road” fell from 28.4% to 25.4%.

As for self-conceived “conservatives,” they too dropped off from 15.2% to 11.5%.

Even at private Catholic and other Christian colleges and universities, “conservatives” and those on the “far right” constitute a tiny minority.

Only 0.3% of the faculty of Catholic institutions locate themselves on the “far right,” compared to 7.8% who identify with the “far left,” and only 13.3% self-identify as “conservative,” compared to 48.0% who self-identify as “liberal.”

At private non-Catholic Christian institutions, “conservatives” have a stronger showing than in any other sector. Yet even here they constitute only 23.0% of faculty. On the other hand, “liberals” compose 40.0% of faculty.

And with 7.4% of the faculty identifying as “far left,” the latter has much more of a presence at these private Christian institutions than one would be inclined to think. At any rate, the “far left” has a vastly stronger presence on such campuses than does the “far right,” with which only 0.6% of faculty relates.

Writing for Inside Higher Ed, Scott Jaschik notes that the leftward trends among faculty have persisted for a long time. George Mason University economics professor, Daniel B. Klein, along with Charlotta Stern, note that in 1972, the ratio of Democrat to Republican in humanities and liberal arts departments was about four-to-one. Today, it is more than eight-to-one. Why?

According to Klein and Stern, academia has the characteristic “antecedent conditions” and “symptoms” of the phenomenon known as “groupthink.”

Academics tend to constitute an “insular” and (ideologically) “homogenous” group that, as such, is self-perpetuating, for academics, presiding as they do over decisions pertaining to who will and won’t be permitted to join their insiders’ club, are disposed to admit those who think like themselves.

Moreover, academics labor under the “illusion of invulnerability” and they share a “belief in the inherent morality of the group” to which they belong. However, “heightened uniformity makes the group overconfident.” Consequently, “members take their ideas to greater extremes” but, “facing less testing and challenge,” their “habits of thought become more foolhardy and close-minded.”

This closed-mindedness is solidified via “collective rationalizations.” The authors explain: “Academic professions develop elaborate scholastic dogmas to justify the omission of challenging or intractable ideas.” Thus, words like “‘normative,’ ‘ideological,’ or ‘advocacy’” are used to sweepingly dismiss viewpoints that depart from the mentality of the herd.

Klein and Stern cite Irving Janis, a scholar of groupthink, who remarks that the “reliance on consensual validation” tends to “replace individual critical thinking and reality-testing.”

Another sign that academics have succumbed to groupthink is their propensity to indulge in “stereotypes of Out-Groups.” Again, Klein and Stern allude to Janis: “One of the symptoms of groupthink is the members’ persistence in conveying to each other the cliché and oversimplified images of political enemies embodied in long-standing ideological stereotypes.” Left-leaning academics, as anyone who has spent any amount of time around them can attest, are guilty as sin in this regard: critics are summarily disregarded as “conservatives” or “right-wingers” who, in turn, are associated with the likes of Bill O’Reilly, Rush Limbaugh, George W. Bush, and so forth.

“Self-censorship” and “direct pressure on dissenters” are two other “symptoms” of groupthink—and the academic world exemplifies them in spades.

Self-censorship leads to “preference falsification” as academics that disagree with the consensus, rather than express their views, choose instead to go along to get along. Those who dare to step out of line are coerced, in so many ways, to conform. “As the group’s beliefs become more defective [questionable], the group becomes more sensitive to tension, more intolerant of would-be challengers and miscreants.” Klein and Stern add: “This development leads to tighter vetting and expulsion, more uniformity, more intellectual deterioration, and more intolerance.”

It is not toward women and minorities that philosophy and other fields in the humanities are unwelcoming but, rather, those who refuse to endorse leftist groupthink.